//兼容火狐,IE mouseleave,mouseenter事件
function addEvent(_elem, _evtName, _fn, _useCapture)
{
   if (typeof _elem.addEventListener != 'undefined')
   {
      if (_evtName === 'mouseenter')
         { _elem.addEventListener('mouseover', mouseEnter(_fn), _useCapture); }
      else if (_evtName === 'mouseleave')
         { _elem.addEventListener('mouseout', mouseEnter(_fn), _useCapture); }
      else
         { _elem.addEventListener(_evtName, _fn, _useCapture); }
   }
   else if (typeof _elem.attachEvent != 'undefined')
   {
      _elem.attachEvent('on' + _evtName, _fn);
   }
   else
   {
      _elem['on' + _evtName] = _fn;
   }
}

function mouseEnter(_fn)
{
   return function(_evt)
   {
      var relTarget = _evt.relatedTarget;
      if (this === relTarget || isAChildOf(this, relTarget))
         { return; }
      _fn.call(this, _evt);
   }
};
function isAChildOf(_parent, _child)
{
   if (_parent === _child) { return false; }
      while (_child && _child !== _parent)
   { _child = _child.parentNode; }
   return _child === _parent;
}